Numerous methods have been proposed in the prior art for effecting the conversion of coal into liquid fuel. Present commercial conversion methods conventionally comprise subjecting a coal-oil slurry to catalytic hydrogenation at elevated temperatures and pressures to produce a coal-derived synthetic crude oil distillate. Typically, these methods include an ebullated bed technique wherein a stream of the coal-oil slurry admixed with gaseous hydrogen is passed upwardly through an ebullated bed reactor containing a mass of particulate hydrogen catalyst, thereby ebullating the catalyst particles and promoting hydrogenation of the coal.
Exemplary of such prior art technques are those described in U.S. Pat. Nos. 3,791,957 to Wolk; 3,607,719 to Johnson et al; 3,594,305 to Kirk; 3,586,621 to Pitchford et al; 3,755,137 to Schuman; 3,519,555 to Keith et al; 3,338,820 to Wolk et al; 3,540,995 to Wolk et al; and 3,679,573 to Johnson.
Such techniques, while generally effective in converting coal into the desired liquid product, have characteristically been limited to conversion of the coal. While the desirability of effecting simultaneous conversion of both coal and oil feed components in these ebullated bed procedures has been recognized, for example, to increase the conversion efficiency of the hydrogenation process and to avoid the present necessity for reprocessing the slurry oil stream through the reactor equipment train, effective simultaneous conversion of the coal and oil feedstock components has been generally considered impractical, owing in part to the different reaction conditions thought necessary for the conversion of the separate components, and to the expected incompatibility of the product liquids, particularly those comprising full range distillates boiling up to about 1000.degree. F.
While other techniques have been employed for the conversion of oil and coal, such as the fluidized bed techniques described in U.S. Pat. Nos. 3,870,621 (Arnold et al) and 3,652,446 (Dingler), these techniques have not heretofore generally provided for the effective simultaneous conversion of coal and oil blends.